OBJECTIVES:Evaluate an educational program based on "CLEAR" (Cervical Length Education and Review) in the teaching of measuring sonographic cervical length to residents in gynecology and obstetrics. METHODS:This is a prospective cohort study in a tertiary care center between May and November 2017. The residents were asked to collect 5 cervical length images from patients suspected with threatened preterm labor. A theoretical session on cervix measurement image criteria based on "CLEAR" program was taught to all residents. Then, they had to collect 5 new cervical length images. All the images were reviewed by two experienced reviewers, blinded to the resident and whether the image was obtained before or after the theoretical session and based on 8 criteria. RESULTS:Ten residents participated to the study. The mean total score CLEAR was significantly higher post-intervention: 6.6±0.9 vs. 4.3±2.1, positive difference of 2.3±2.3 (P<0.001). Improvement was most significant with the junior residents: 3.6 pre vs. 6.5 post-intervention. CONCLUSION:Educational program based on CLEAR criteria allowed to improve the competence of residents in measuring sonographic cervical length, although this can also be correlated with the progression of residents during the semester. It could be implemented systematically with the aim of CLEAR certification to standardize the teaching of residents in gynecology and obstetrics.